Telephone system



Jan. 13, 1925.

A. E. LNDELL TELEPHONE SYSTEM Filed Oct. 24. 1919 Patented Edan. if, 1925.

naiven stares @ENCE ALBEN E. L'UNDELL, OF NEW YORK, N. Y., ASSIGNOEL TO WESTERN' ELECTRIC COM- PANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION 0F NEW YORK.

TELEPHONE SYSTEEYI.

Application filed Gotober 24, 1919.

To all whom t may concern.'

Be it known that l, ALBEN E. LUNDELL, a citizen of the United States, residing at New York, in the county of Bronx, State of New York, have invented certain new and useful Improvements in rIelephone Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to improvements in telephone exchange systems, and has particular reference to a system in which machine switching is employed.

It is customary in switches employing a plurality of brushes designed to pass over terminals of a bank in selecting a line or trunk, to engage said brushes with the respective terminals upon each step 'of the switch. This operation has been found to produce considerable friction between the contacting elements resulting in a retardation of the speed of the switch.

The object of the present invention is to reduce the friction to a minimum, thus permitting of an increased speed yof selection.

In accordance with this object, the shaft of the switch which carries the brushes is initially moved to position certain of said brushes so that the same will not engage their associated terminals in the bank during the secondary movement of the shaft or trunk hunting operation. The initial movement of the shaft is also utilized to position a test brush so that the same will engage the terminals of its associated row during the secondary movement and thus accomplish the selection of an idle trunk whereupon the shaft is given a tertiary movement to cause engagement of the first named brushes with the terminals individual to the selected trunk.

The inventive idea involved is capable of receiving a variety of expressions, one of which, for the purpose of illustrating the invention, is shown in the accompanying draw ing; but it is to be expressly understood that said drawing is employed merely for the purpose of facilitating the description ofthe invention as a whole and not to define the limits thereof, reference being had to the appended claims for this purpose.

The drawing illustrates a line switch and circuits for operating the same, arranged in accordance with the invention.

Although the invention is illustrated as Serial No. 332,879.

applied to a line switch, it will be understood, of course, that same may be employed with equal facility in switches of different character without departing from the spirit of the invention. i

The switch comprises a shaft 1 slidably and rotatably mounted in bearings 2 and 3 and held in position therein by means of a supporting arm 4, the free end of which engages the lower end of said shaft. A coil spring 5 is connected to the arm 4, in such manner that the same will exert a constant upward pressure upon the shaft to normally maintain it in an elevated position. The shaft 1 carries a test brush 6 and a series of other brushes 7, the brush 6 being normally spaced from its test terminals 8 and preferably made of flexible metal, so that when the same is passing over said terminals in the bank of the switch the friction between the contacting elements will be reduced to a minimum.

An operating magnet 9 is provided and has one end of its armature 10 secured to the shaft 1 while the other end thereof is curved and tapered as indicated at 11. The free end 11 of the armature 10 is normally offset with respect to the core of magnet 9 and arranged above the same in such manner that, upon energization of said magnet, the al1-mature 11 will be initially attracted in a downward direction whereby the shaft 1 will be moved longitudinally in its bear ings 2 and 3 against the tension of the spring 5. This movement will disengage brushes 7 from their respective terminals and engage test brush 6 with a terminal in its associated row. The energization of magnet 9 will, at the same time, attract the armature 10 so as to impart a rotary or secondary movementto the shaft 1 which will have the effect of engaging test brush 6 with the row of terminals 8. The movement of the armature 10 and the consequent rotation of the shaft 1 is sufficient to engage brush 6 with all of the terminals in its associated row. This movement continues until brush 6 engages a terminal to which an idle trunk is connected whereupon the cut-oft' relay 12 of the switch which is slow to release is energized to engage pawl 13 with the ratchet 14 carried by the shaft 1, adjacent its upper end. This engagement of pawl 13 with ratchet 14 will prevent a return of the shaft 1 to normal position under the influence of the spring 15 which is tensioned as said shaft is rotated during the trunk hunting operation. Energization of the cut-off relay 12 opens the energizing circuit for magnet 9 so that the armature 10 thereof will be released for movement in an upward direction. `lVhen the armature is released, spring 5 will exert sufficient power upon the supporting arm 4 to start the shaft 1 upwardly until the brushes 7 engage the associated terminals which are individual to the idle trunk selected. The upward movement of the shaft will not disengage ratchet 14e from pawl 13 as the latter is made suliicient-ly wide to engage the teeth of the ratchet at all times during the energization of relay 12. An upward movement of the shaft will also disengage the test brush 6 from its associated terminal.

It is believed that the invention will now be fully understood from the following detailed description of the operation.

When a subscriber at substation 16 removes his receiver from its switchhook to initiate a call, a circuit is established for line relay 17 extending from grounded battery, winding of said relay, back contact and outermost left armature of cut-off relay 12, the apparatus at substation 16, and the next to the outermost left armature and back contact of relay 12 to ground. Relay 17 energizes and thereby establishes a circuit extending from grounded battery, armature and front contact of relay 17, winding of operating magnet 9, and next to the innermost left armature and back contact of relay 12, to ground. This circuit energizes magnet 9 which, in attracting its armature 10, initially moves the same in a downward direction to give the shaft 1 a similar movement, whereby the brushes 7 are moved to a position where the same will not contact the associated terminals during the trunk hunting operation of the switch. At the same time brush 6 is moved into engagement with the first terminal 8 of its associated row so as to test for an idle trunk extending to a succeeding switch. Continued energization of magnet 9 will also move its armature in a rotary direction so as to impart a similar movement to the shaft 1 whereby the brush 6 will be made to engage the terminals of its row. As the shaft 1 rotates, spring 15 is tensioned so that at the termination of a call and when said shaft is released, the same will be rotated to its normal position.

'lhe busy condition of a next succeeding switch is denoted by the opening of the olfnormal contact 18 which is closed when the switch is idle. The brush 6 will therefore be rotated over the terminals 8` until the same engages a terminal connected to a switch having the olf-normal contact 18 thereof closed. An energizing circuit will then be established for cut-oft' relay 12 extending from grounded battery, armature and front contact of relay 17, right winding of relay 12, brush 6, terminal 8, conductor 197 and olf-normal contact 18, to ground. By attracting its right armature, relay 12 operates the pawl 13 to engage the ratchet 14; and thereby prevent any rota-ry movement of the shaft 1 towards its normal position. The attraction of the two middle lefthand armatures of relay 12 opens the circuits for magnet 9 and relay 17 which thereupon deenergize. Release of relay 17 opens the energizing circuit of relay 12 but this relay being slow to release does not immediately deenergize. Release of magnet 9 permits of a slight upward longitudinal movement of the shaft 1 under the infiuence of the supporting arm 4 and spring 5. This upward movement reengages brushes 7 with their respective terminals to which the idle trunk is connected. Vhen the lowermost brush 7 engages its terminal a locking circuit is established for relay 12 extending from grounded battery, armature and back contact of release magnet 2O of the next succeeding switch, which remains deenergized throughout the 'duration of the call, terminal 21, lowermost brush 7, brush contact and innermost left armature of relay 12, and the left winding of said relay to ground. Energization of cut-olf relay 12 also extends the calling line through the two outermost left armatures and front contacts of said relay and the two uppermost brushes 7 to the trunk connected with the next succeeding switch.

When the subscribers replace their receivers upon the switchhooks at the termination of the conversation, the release magnet 20 of said next succeeding switch is energized in a manner well known in the art, and in attracting its armature opens the locking circuit for cut-olf relay 12. When relay 12 releases, pawl 13 is moved out of engagement with the ratchet 141 and shaft 1 is permitted to rotate to its normal position due to the action of the spring 15. The parts of the switch will then be restored and in position to extend another call. Should substation 16 be called, engagement of a brush of a final connector with the terminal 22 will in the event the line is idle, extend battery in the usual manner through the left winding of relay 12 to ground and thus causes this relay to energize to prevent energization of relay 17 when the subscriber at substation 16 removes his receiver in response to the call. If the line is busy when the call is extended to substation 16, this condition will be indicated on terminal 22 by the battery potential extending through the armature and contact of relay 20 and the front contact and innermost left armature of relay 12.

What is claimed is:

1. In a telephone system, a calling line, a switch for extending said line, a shaft for said switch, brushes carried by said shaft, a group of trunks associated with said brushes, means for operating said shaft to disengage certain of said brushes from ass0- ciated terminals of said trunks and to engage another brush with associated terminals during the trunk hunting movement of said switch, and means for engaging the first named brushes with the associated terminals when an idle trunk is found.

2. In a telephone system, a calling line, a switch for extending said line, brushes for said switch, a shaft carrying said brushes, a terminal bank for said switch, means for initially moving said shaft to disengage certain of said brushes from terminals of said bank with which they are associated, for engaging another of said brushes with other terminals of said bank and for giving the shaft a secondary movement to pass said latter brush over the terminals associated therewith, and means for imparting a tertiary movement to said shaft whereby the first named brushes are engaged with associated terminals.

3. In a telephone system, a calling line, a switch for extending said line, a shaft for said switch, brushes carried by said shaft, a group of trunks associated with said brushes, an operating magnet for said switch having an armature secured to said shaft, means for energizing said magnet to attract its armature whereby said shaft is given an initial movement to disengage certain of said brushes from associated terminals of said bank and to position another brush in operative relation with respect to other teri minals, the attraction of said armature by said magnet being also adapted to rotate said shaft whereby the last named brush is passed over associated terminals, and means for moving said shaft to reengage the first named brushes with associated terminals when the said other brush engages a terminal connected to an idle trunk.

In witness whereof, I hereunto subscribe my name this 18th day of October, A. D.,

ALBEN E. LUNDELL. 

